The present invention generally relates to a heater for titration plates and more particularly pertains to a heating device that is capable of exclusively thawing the contents of individually selected sample wells within a titration plate.
Titration plates are commonly employed in laboratory work of various disciplines to store multiple samples, typically in a closely spaced 8.times.12 pattern of sample wells. The titration plate is often of monolithic construction and may comprise a single injection molding of a chemically inert plastic material. Each individual well extends downwardly from the flat top face of the plate, is typically cylindrical in cross-section and is provided with a flat, U-shaped or V-shaped bottom to support a sample volume of 1 ml.
Titration plates offer a convenient means for processing large numbers of samples such as, for example, when used in a screening process, a statistical analysis or a large-scale assay project. It is often necessary to maintain the titration plate in a frozen state in order to preserve or stabilize the contents of the individual sample wells. A distinct disadvantage inherent in the use of the described titration plate becomes apparent when only one or just a few, or in fact any number less than all of the frozen sample wells need to be accessed. In order to do so, it has previously been necessary to thaw out the entire titration plate including all of the samples contained therein. After extraction of the desired sample, the rest of the samples are refrozen for future use. This process can have a detrimental effect on such samples as the residence time in their thawed state is extended while the thermal cycling and repeated phase changes can pose additional problems. Handling, while in the thawed state, also increases the risk of spillage and contamination.
While thawing is typically accomplished by simply removing the titration plate from the freezer and allowing the ambient temperature in the laboratory to warm up the samples, heating devices have been previously devised to expedite the thawing. The amount of time the samples are in their unfrozen state may be somewhat reduced thereby, but the samples are still subjected to the potentially detrimental thermal cycling and phase changes. A simple hot plate fulfills the most fundamental requirements while the more sophisticated heating devices include features that endeavor to maintain as uniform a temperature as possible throughout the entire array of samples contained in the titration plate. Additionally, heating devices are known that subject the entire array of sample wells in a titration plate to a prescribed temperature gradient as is useful for any of a variety of analytical purposes.
The prior art is devoid of a device that is capable of facilitating access to an individual sample well of a titration plate without disturbing the frozen state of those sample wells that are not to be accessed.